The Alternative Indoor Air Standard

I'm working in an area that may exceed the indoor air standard (0.01 f/cc). Is there anything I can do about this?

If you suspect elevated fiber levels in the area where asbestos work is going to be performed, you have the option of taking five preliminary or background air samples to establish an alternative indoor air standard. These preliminary air samples must be taken simultaneously and analyzed before any other asbestos-related work begins, including area preparation. The samples must be taken within ten feet of where the work area will be. An alternative indoor air standard can be established for full containment, glove bag or mini-containment work. You will need separate alternative indoor air standards for each full containment. For glove bags or minicontainments operations, you may establish an alternative indoor air standard in each room where these operations are taking place, or in some industrial facilities, each 15,000 square foot area of floor space.

The analytical results of at least one sample must be greater than the Minnesota indoor air standard of 0.01 fiber per cubic centimeter (f/cc) of air in order to establish an alternative indoor air standard.

How do I establish an alternative indoor air standard?

The alternative indoor air standard must be calculated as the upper bound of the range defined by the 95 percent confidence interval from the mean of the results of the five samples.

95% Confidence Limit = x + (1.645 * σ)

To calculate the mean,

mean = x = ¹/₅ * (S₁+S₂+S₃+S₄+S₅)

where S_n is the concentration in f/cc of the five preliminary samples.

To calculate the standard deviation, σ

σ = √{¹/₅ * [(S₁-x)²+(S₂-x)²+(S₃-x)²+(S₄-x)²+(S₅-x)²]}

How do I find out more information?

For more information about asbestos, contact the Asbestos Program at MDH through the internet or by telephone at (651) 201-4620.